Souza -- Washington's No. 5 prospect -- more than likely will come off the bench and may get an occasional start. McLouth injured his shoulder making a diving play in a 7-6 loss to the Marlins on July 28.
McLouth, who signed a two-year deal in the offseason, is hitting .173 with one home run and seven RBIs.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.